Dedicated to Joaquim L. Matheus for 20 years of tremendous help in the lab.
Abstract
Nearly two decades of work on ring-contraction reactions is discussed in this account.
We have developed several reliable protocols for the rearrangement of a number of
different substrates using thallium(III) salts and, more recently, hypervalent iodine(III)
reagents. A variety of ring systems, such as cyclopentanes, cis - and trans -hydrindanes, and indanes, can be obtained using these methods. Additionally, the
stereoselective total syntheses of the sesquiterpenes (±)-, (–)- and (+)-mutisianthol
and (+)-bakkenolide A, the indole alkaloid (±)- and (+)-trans -trikentrin A, and the potential drug (±)-indatraline have been achieved through a
ring-contraction approach.
1 Introduction
2 Ring-Contraction Reactions Promoted by Thallium(III)
2.1 Thallium(III)-Mediated Ring Contraction of Cyclic Ketones
2.2 Thallium(III)-Mediated Ring Contraction of Cyclic Olefins
2.3 Thallium(III)-Mediated Ring Contraction of Homoallylic Alcohols
3 Ring-Contraction Reactions Promoted by Iodine(III)
4 Conclusion
Key words total synthesis - ring contractions - oxidative rearrangements - thallium(III) - hypervalent
iodine
